rTMS for Lower Limb Hemiparesis after Stroke

Abstract

For the treatment of lower limb hemiparesis after stroke, it is desired to activate lower limb regions of the primary motor area on both sides. A double cone coil has a deep focus of stimulation and can stimulate such regions located in the deep. For gait disturbance after stroke, therefore, we introduced high-frequency rTMS using a double cone coil placed on the cranial median line, combined with physical therapy including treadmill training. This combination protocol seemed to be beneficial for such neurological symptoms.

Appendix: Intensive Physical Therapy That Should Be Used in Combination with rTMS

Lower Limb Dysfunction and PT in Poststroke Hemiparesis

The following discusses a mechanism that may occur if rTMS on an upper limb has influenced lower limb function.

In PT, the severity of poststroke hemiparesis is determined by the Brunnstrom recovery stages (BRS) (Table 5.5) [12, 13]. The staging is intended to facilitate judgment on whether or not a limb can move and perform isolated movement. In a normal condition of “isolation,” the person can do a simple exercise and move his/her hands, legs, and fingers independently at will. Separation can be an important criterion to decide whether a limb is in a normal condition. Nonisolation does not always mean a state in which a limb cannot move at all.

Table 5.5 Brunnstrom recovery stage (lower limbs and trunk)

In BRS, Stage IV or higher means isolation is recognizable. However, it is hard to discern the conceptual reduction of spasticity from the expression of isolation. Judgments as rule of thumb cannot be ruled out. If the muscle tone has increased, it is often the case that the expression of isolation is inadequate. In particular, it has much to do with factors such as posture, action, and move. Under load, abnormality of muscle tone uniformly becomes apparent. Differences between Stage IV and V should be decided by observing the same joint movement performed in different postures. In other words, this means isolation is strongly influenced by an increase in postural muscle tone.

The postural muscle tone allows a hemiparesis patient to move the upper limb, which is relatively relaxed in a supine position, to take a specific posture in the upright position or while walking.

This is the so-called Wernicke-Mann leg position. Its characteristics are more apparent in a sitting position than in a supine position and while walking than while sitting. An increase in the muscle tone in the upper limb influences movements of the trunk and lower limbs.

A gait of a human being is phylogenetically differentiated from that of other vertebrates by the movement of the trunk when crawling on hands and knees. This can be explained, in an arthrokinematic manner, as a smooth and alternate rolling and sliding movement based on the retention of centripetal force, and kinematically as a phase movement where the limbs swing alternately. When an upper limb swings forward, the lower limb on the opposite side makes a step forward. When an upper limb swings backward, the lower limb on the opposite side is guided to the toe-off position through the stance phase. In other words, a gait consists of regular movements in which upper limbs and lower limbs move in opposite phases. A forward movement is accompanied by an axial rotation around the trunk (Fig. 5.10).

Fig. 5.10

Opposite phases of a human gait.

When the left leg makes a step forward, the right hand swings forward. When the right leg makes a step forward, the left hand swings forward

Opposite phases with left-right alternate movements require the upper limbs to swing and the lower limbs to take a step. The more poststroke hemiparesis makes isolation insufficient, the more it strategically supplements a compensatory function that replaces the functions of the upper limbs and trunk that are necessary for walking. Worse, abnormality in muscle tone makes it hard to form a smooth cycle. As a consequence the gait cannot be symmetrical, and the gait of the patient with stroke takes on characteristic patterns such as extension thrust pattern (a pattern in which the knee is overextended), stiff knee pattern (a pattern in which a stiff knee results in less flexion), and bucking knee pattern (a pattern in which the knee is overflexed). An abnormal gait pattern lacks efficiency and burdens the cardiopulmonary function. As a consequence, the patient slows walking speed to stabilize, and the possibility of secondary complications such as falls and pain increases.

Here, it is worth noting that the effects of rTMS treatment demonstrated by Abo et al. [14–18] through a study with a rat model can be explained as follows: functional compensation in the lesional hemisphere and in the residual regions around the lesion, not in the nonlesional hemisphere on the nonlesional side, plays an important role in the partial involvement within an adult’s brain that concerns recovery from paralysis. For tissues around the lesion of the affected brain that are considered to facilitate functional recovery, low-frequency stimulation on the nonlesional hemisphere is reported to have reduced interhemispheric inhibition and activated functional compensation.

In fact, the effects of rTMS on upper limb hemiparesis are reported. Given the above mechanism of a human gait, the effects of rTMS on reducing muscle tone in the upper limbs may also bring about a change in gait that requires coordination of the upper and lower limbs.

Usefulness of Treadmill Gait Training

A gait is an unconscious movement and is based on a reflexive mechanism. It is considered that a gait can be divided into three different phases as a stratified control (Fig. 5.11) [19]. The first phase involves planning and preparation for movements in the cerebrocortical motor area. The second phase involves coordination by the brain stem. The third phase is characterized by control by the central pattern generator (CPG) consisting of a group of spinal interneurons. CPG does not involve voluntary control by the cerebrum and is coordinated in a reflexive manner. While walking, a person does not think about when to move the other leg forward every time he or she takes a step. Every step is not based on intentional adaptation to a command to contact the ground or floor with a heel. Voluntary control by the cerebrum is limited to adaptation to a signal or changes in road surface, unevenness of the floor or ground, and similar.

Fig. 5.11

Diagram of stratified control [8]

When walking on a flat surface, a patient with hemiparesis moves a leg forward and contacts the ground or floor with a good clearance and keeps the feet supporting the body to prevent falls, before shifting his/her center of gravity toward the opposite side, the nonparalyzed lower limb. While walking, a patient with hemiparesis remains conscious about these procedures. In particular, consciousness about these procedures is greater in patients with problems such as sensory impairment, weakened muscle strength in the nonparalyzed lower limb, and fear that comes from advanced age. These people are more likely to stop walking before stepping over a bump or passing someone. Many of these people walk asymmetrically by leaning the trunk forward and leaning the pelvis backward to flex the hip joint with a center of gravity on the nonparalyzed lower limb. Even the coordination of pace is based on the patient’s will. It is not always the case that doing a lot of walking every day will facilitate recovery. To induce a qualitative effect, a physical therapist gives visual stimulation with the use of oral instructions, a mirror or a video, shows changes in time-distance factors, and combines them with handling in an effort to bring about alteration. In fact, the authors do this in clinical practice. It is difficult to scientifically verify this type of intervention in a gait.

On the other hand, walking on a treadmill involves the floor surface shifting backward at a constant speed, providing a kind of gait using passive stepping. In terms of floor reaction force waveform overall, walking on a treadmill involves greater similarity than walking on a flat surface does [20]. Despite differences in minor parameters, it is considered to be possible to diagnose and determine the degree of amelioration of gait disturbances with the use of a treadmill [21].

For a period of time after starting a treadmill, the patient continues to focus on movements (stimulation) on the floor surface and may feel insecure at times. Since the treadmill gait training is provided in a stepwise manner, the patient gradually adapts him/herself to the changeless and constant stimulation. This may facilitate a shift from the conscious movements of legs to unconscious movements. This is a clear difference from walking on a flat surface where stimulation occurs randomly and in many different forms. It is also important that the treadmill gait training ensures physical therapists sufficient time for observation.

Studies of paraparesis induced by spinal cord injury have confirmed some effects of walking on a treadmill. For example, walking on a treadmill may exert effects in the form of induction of muscle activity in harmony with a walking cycle [22] or achievement of a hip extension position in the late stance phase [23]. In addition, using a treadmill serves as an opportunity for a hemiparesis patient to become aware of a left-right gap in his/her gait cycle. In patients whose muscle tone in the upper limb has been reduced after rTMS, using a treadmill may influence upper limb swings and the rotation of a trunk and, consequently, make it possible to swing a lower limb and to achieve a standing position within an area of hip joint extension. Compared with walking on a flat surface that is a patient-steering movement, walking on a treadmill is a passive movement adapted to an automatically moving surface. The use of a treadmill may be expected to help improve ambulatory ability through the indirect effects of reduction of muscle tone in the upper limbs and trunk, provided that rTMS has reduced the tension in the upper limbs and made it easier for isolation to express.

In today’s healthcare and welfare practices, aggressive PT is becoming increasingly hard to perform with patients in the maintenance period. Many patients engage in self-exercise as a part of their daily life. The Japanese Guidelines for the Management of Stroke 2009 [24] recommends rising and walking for rehabilitation in the maintenance period. However, it is hard for a patient alone to concentrate on a specific instruction without receiving advice. This is especially true for patients with hemiparesis in the generation to which long-term care insurance services do not apply. We hope that rTMS will play the role of a means of preconditioning in performing intensive PT for patients who continue training on their own.